Until recently, a woman diagnosed with cancer had to choose between starting treatments immediately or waiting while she could preserve her fertility.

If a woman wanted to collect her eggs to be stored for later, she would have to wait until the right time in her cycle. "If she was not at the beginning of her cycle right after her period, we would have to wait until the next period," says Dr. Shahryar Kavoussi, a reproductive endocrinologist at St. David's South Austin Medical Center.

Kavoussi says there was this dogma that the follicles would be too small and not viable for fertilization if doctors didn't wait until the start of the cycle.

It then became a point of contention between the oncologist and the fertility specialist, he says. "If we're going to pick someone's life or eggs, we would pick the woman and make sure she's OK," he says.

And that meant that many women started cancer treatment before they could collect eggs and thus ended the chance of later having a biological child because cancer treatments would cause infertility.

The new line of thinking, which started around 2013, is that there are waves of fertility. A woman can start the shots to stimulate the growth of follicles at any point in her cycle as long as her hormones are in the right range. It usually takes about eight days of shots to grow the follicles, and then they can be collected, and she can start her treatment. 

New drugs also help. Letrozole, which has been used as a cancer inhibitor in estrogen-responsive cancers such as breast cancer, also has a use in fertility treatments. It allows women to grow follicles but keeps the estrogen peaks low, which reduces the risk of feeding the cancer as she grows follicles for collection.

Doctors are also doing innovative things such as collecting ovarian tissue samples to freeze and then transplant back into a woman after her cancer treatments are finished.

Fertility preservation can be expensive, costing several thousands of dollars to stimulate follicle production and collect follicles and freeze them. Most insurance doesn't cover this, Kavoussi says, but LiveStrong Foundation helps patients receive the fertility medication to reduce costs. "We do everything we can to find a way to get this done because it's cancer," Kavoussi says.

After a woman goes through treatments and is in remission for several years and her oncologist clears her, Kavoussi and his team can start the in vitro fertilization process with the frozen follicles.

The biggest change, Kavoussi says, is that they don't have to wait for her cycle to collect eggs. The outcomes as far as children born from these eggs, he says, are basically the same as the previous way of doing things.